This study is about the symbolism of Millstone appeared in psychotherapy like sand play therapy with symbol work. Symbols not only deliver meanings but also have numinous power, which produces transformation through powerful energy from emotional experience. Symbols help human’s mentality develop by compromising opposites which cause conflict. This study is to examine the characteristic of Millstone in human history and the symbolic meaning which appears in mythology and tales and alchemy, and to explain universal and cultural meaning of millstone connected to psychological symbolism. Millstone represents pain through sacrifice of grain, death and the creation of new consciousness as a symbol of the rebirth. Also, it explains the circulation of original nature as a symbol of destiny to overcome by the integration of anima and animus. The millstone described as the symbol of Self in the marriage of mythology represents the coniunctio oppositorum between men and women, a combination of yin and yang. It is the symbol of wholeness integrating conscious and unconscious. Through this study, we consider that millstone is the psychic center of the ego- Self axis and the individuation in the psychotherapy is the process of unceasing transformation of one’s whole personality which experiences the process of balancing, regulating and unifying. Consequently, millstone functions as symbolic intermediation that leads to the center of one’s whole psyche.